1. Field of Invention
The present invention relates to fuel cell, and more particularly to an integrated end-bus plate which provides electrical conduction and manifolds for fluid flowing in one body for a fuel cell stack so as to prevent fluid leaking between the end plate and the bus plate and the formation of metallic ions due to the electrochemical corrosion of the bus plate that generally results in causing damages to the fuel cell.
2. Description of Related Arts
Electrochemical fuel cell is a kind of electrochemical energy conversion device which is capable of converting hydrogen and oxidant into electrical energy. Proton exchange membrane fuel cell can be used as the power supply system of transportation tools, such as land and water vehicles, or a mobile or stationary electric generator.
The core element of the proton exchange membrane fuel cell system is the membrane electrode assembly (MEA) which comprises a proton exchange membrane sandwiched between two porous sheets made of conductive material, such as carbon tissue. In the typical proton exchange membrane fuel cell system, the MEA is disposed between two electrical conducting electrode plates, wherein the contacting interface of each electrode plate provides one or more flowing channels for respectively directing fuel and oxidant into anode side and cathode side which are positioned on opposite sides of the MEA. For a single fuel cell, only one MEA is provided and disposed between an anode plate and a cathode plate. It is noted that the anode plate and the cathode plate are embodied not only as current-collecting device, but also as a supporting device for securely holding the MEA in position.
To increase the overall power output of a fuel cell system, a plurality of fuel cell units are electrically connected in series or in parallel to form a proton exchange membrane fuel cell stack. By incorporating such a proton exchange membrane fuel cell stack with other operation system can build a proton exchange membrane fuel cell power generator.
Referring to FIG. 1, a MEA of the fuel cell unit of the conventional proton exchange membrane fuel cell stack is illustrated, which provides an air inlet manifold 1a, a water inlet manifold 2a, a hydrogen inlet manifold 3a, a reaction region 4a, an air outlet manifold 5a, a water outlet manifold 6a, and a hydrogen outlet manifold 7a therein. Referring to FIG. 2, an electrode plate of the fuel cell unit of the conventional proton exchange membrane fuel cell stack is illustrated, which provides an air inlet manifold 1b, a water inlet manifold 2b, a hydrogen inlet manifold 3b, an air outlet manifold 5b, a water outlet manifold 6b, a hydrogen outlet manifold 7b, and a fluid flowing channel 8b therein.
Referring to FIG. 3, a fuel cell stack comprising a plurality of fuel cell units stacked in series is illustrated, which includes two end plates 9a, a first bus plate 10a, a second bus plate 12a, a plurality of fuel cell units 11a stacked between the first and second bus plates 10a, 12a, and a power load 13a electrically connected between the first and second bus plates 10a, 12a. 
FIG. 4 illustrates a proton exchange membrane fuel cell stack which includes a plurality of sets of fuel cell stack electrically connected in parallel with a power load, wherein each set of fuel cell stack comprises a first bus plate 10b, a second bus plate 12b, and a plurality of fuel cell units 11b stacked between the first and second bus plates 10b, 12b. In addition, the proton exchange membrane fuel cell stack further include a plurality of insulation plates 14b each of which is sandwiched between the bus plates 10b, 12b of two sets of fuel cell stack.
Each type of fuel cell stacks as shown in FIGS. 3 and 4 consist of two or more bus plates functioning as anode and cathode of an external electric circuit and outputting an electric current from couple fuel cell units stacked in series or parallel manner or from a fuel cell stack to construct the electric circuit.
In addition, each of the bus plates has various fluid manifolds provided therein to enable various fuel cell fluids flowing therethrough. Referring to FIG. 5, the bus plate 10c as shown has fluid manifolds 1c, 2c, 3c, 5c, 6c, and 7c and two current output terminals 15c. Except the two current output terminals 15c, the bus plate 10c substantially has the same size of the end plate of fuel cell stack while all fluid manifolds provided in the bus plate 10c have the same shape and size of that of the end plate so as to define various flowing passages of the whole fuel cell stack.
In order to achieve the above two features, the conventional bus plate of all kinds of fuel cell stack is made of noble metals such as gold, platinum or other metals such as stainless steel, copper or aluminum electroplated with gold or platinum. These noble metals not only have good conductibility but also can avoid electrochemical corrosion and thus will not produce any metallic ions that may cause damages to the fuel cell stack. However, these noble metals are very expensive. Even using stainless steel, copper or aluminum electroplated with gold or platinum is still relatively expensive and inconvenience.
If stainless steel, copper or aluminum is directly used to make the bus plate, electrochemical corrosion will occur when various fuel cell fluids passing through the fluid manifolds resulting in unwanted damages to the fuel cell stack due to the metallic ions produced.